1. Field of the Invention
The present invention relates to a vehicle tack-in prevention control device having a traction control function of preventing slipping of driving wheels by reducing the over torque amount of the driving force calculated from a driving state of a vehicle, and a tack-in prevention control function of exerting tack-in prevention control when the accelerator opening is less than or equal to a predetermined value during turning of the vehicle. More particularly, the present invention relates to a vehicle tack-in prevention control device that properly prevents a tack-in phenomenon when traction control is exerted.
2. Description of the Related Art
When an accelerator pedal is released in a state in which the lateral acceleration is high, the cornering force of the front wheel side increases, and this may sometimes cause a tack-in phenomenon. In an all-wheel drive vehicle in which the longitudinal driving-force distribution can be changed by electronic control, the release of the accelerator pedal during turning is detected by an accelerator-opening sensor, and a front-rear driving-force distribution control unit is controlled so as to generate a yaw moment in a direction opposite the turning direction, thereby suppressing a tack-in phenomenon (tack-in prevention control) (for example, see Japanese Unexamined Patent Application Publication No. 2006-341828).
In the above-described publication, since tack-in prevention control is triggered by the accelerator opening, it can be exerted earlier before a vehicle behavior appears than the control triggered by the throttle opening. Therefore, it is effective to use the accelerator opening as a trigger for tack-in prevention control.
Traction control is known which reduces the driving force when the driving wheels are slipping or are likely to slip. However, when traction control is exerted during turning of the vehicle, the grounding load on the front wheels is increased by the reduction of driving force, and the cornering force of the front wheels is increased. In this case, a tack-in phenomenon may be promoted by traction control. For this reason, in a case in which tack-in prevention control is triggered by the accelerator opening that is dependent on the driver's operation, as in the technique disclosed in the above publication, even when traction control starts during turning of the vehicle, tack-in prevention control does not start unless the driver releases the accelerator pedal. Therefore, there is a fear that a tack-in phenomenon will not be prevented effectively. In particular, when traction control starts and the speed of the vehicle decreases, the driver does sometimes not operate the accelerator. Accordingly, the probability that tack-in prevention control will not start increases.